A septic tank or domestic sewage treatment plant will treat wastewater from premises which are not connected to the mains drainage system. This wastewater includes toilet waste, sink waste, shower waste, sink waste etc.
Septic tanks and sewage treatment plants come in all shapes and sizes. However, traditional, or older, tanks are usually rectangular structures made of brick, stone, concrete
buried in the ground. More modern tanks can be made from plastic or fiberglass, shaped like an onion or a large rectangle.
A septic tank works as a passive system powered entirely by gravity. Simple sewage treatment plants may rely on a pump which is positioned inside or a separate pump chamber outside the main tank to replace the force of gravity for discharge through a drainage field.
All household wastewater flows into the septic tank at one end. Solid waste material is allowed to settle in the septic tank and is digested by natural bacteria which must be allowed to breed within the septic tank. As new water enters the septic tank, it displaces the water that's already there. This treated effluent drains from the septic tank’s outlet pipe, normally to a drainage field system.
In a traditionally constructed septic tank there are three layers of waste; anything that floats rises to the top of the septic tank and forms a layer known as the Scum Layer. Anything heavier than water sinks to the bottom of the septic tank to form the SludgeLayer. In the middle is a fairly clear water layer with some suspended particles. This water contains bacteria and chemicals like nitrogen, phosphorous and ammonia which act as a fertiliser, but it is largely free of solids.
Over time partially-decomposed solids build up on the bottom of the septic tank. This sludge has to be cleaned out regularly to make sure the tank continues to work properly and to prevent the drainage field becoming choked. Emptying out the septic tank should normally take place every twelve months.
Why you need to get your septic tank or domestic treatment plant sludge emptied every year:
By emptying your septic tank once per year will help to reduce the risk of blockages and damages which can be very expensive and time consuming to fix. The cost of emptying and cleaning a septic tank can cost £180 - £280 but to fix or replace a septic tank will cost between £10,000 and £20,000. So having the septic tank emptied every year is a bit like insurance.
The guidance from the Environment agency is to empty the tank once per year to ensure no environmental contamination or damage is caused. If septic tanks are malfunctioning then there could be a leak which causes damage to the surrounding environment.
By emptying the septic tank once per year you can reduce the smells emanating from the tank. If there is a large quantity of sludge within the tank then there will be smells.However, if it is emptied and cleaned out regularly then there shouldn’t be any smells.
Nobody wants their house toilets and baths to be blocked or backed up with foul smelling waste. If aseptic tank becomes too full of sludge then it may prevent new waste from entering the septic tank which causes your pipes to block and therefore waste will back up into your house.